(1) Field of the Invention
The present invention relates to a liquid crystal display device, and more specifically to a liquid crystal display device in which a color filter and an active device are disposed on the same substrate.
(2) Description of the Related Art
A liquid crystal display device includes an upper substrate provided with a color filter and a black matrix and a lower substrate provided with an interconnection and an active device, and a liquid crystal is provided between the upper and lower substrates. In such a liquid crystal display device, it is extremely difficult to align the color filter with the active device, easily causing a decrease in color mixture and a decrease in the aperture ratio. In order to solve such problems, a color filter on array (COA) technology is used in which a color filter and an active device are formed on the same substrate.
Japanese Unexamined Patent Application Publication No. 2002-350886 describes a display device in which on one of substrates, a color filter is provided on a protective film for an active device, a contact hole is formed on the color filter and the protective film for the active device, and then the pixel electrodes of the active devices are connected to each other.